tapping with stats_tree Let's suppose that you want to write a tap only to keep counters, and you don't want to get involved with GUI programming or maybe you'd like to make it a plugin. A stats_tree might be the way to go. The stats_tree module takes care of the representation (GUI for Wireshark and text for TShark) of the tap data. So there's very little code to write to make a tap listener usable from both Wireshark and TShark. First, you should add the TAP to the dissector in question as described in README.tapping . Once the dissector in question is "tapped" you have to write the stats tree code which is made of three parts: The init callback routine: which will be executed before any packet is passed to the tap. Here you should create the "static" nodes of your tree. As well as initialize your data. The (per)packet callback routine: As the tap_packet callback is going to be called for every packet, it should be used to increment the counters. The cleanup callback: It is called at the destruction of the stats_tree and might be used to free .... Other than that the stats_tree should be registered. If you want to make it a plugin, stats_tree_register() should be called by plugin_register_tap_listener() read README.plugins for other information regarding Wireshark plugins. If you want it as part of the dissector stats_tree_register() can be called either by proto_register_xxx() or if you prefer by proto_reg_handoff_xxx(). A small example of a very basic stats_tree plugin follows. ----- example stats_tree plugin ------ /* udpterm_stats_tree.c * A small example of stats_tree plugin that counts udp packets by termination * 2005, Luis E. G. Ontanon * * Wireshark - Network traffic analyzer * By Gerald Combs * Copyright 1998 Gerald Combs * * SPDX-License-Identifier: GPL-2.0-or-later */ #include "config.h" #include #include #include static int st_udp_term; static gchar* st_str_udp_term = "UDP terminations"; /* this one initializes the tree, creating the root nodes */ extern void udp_term_stats_tree_init(stats_tree* st) { /* we create a node under which we'll add every termination */ st_udp_term = stats_tree_create_node(st, st_str_udp_term, 0, STAT_DT_INT, TRUE); } /* this one will be called with every udp packet */ extern tap_packet_status udp_term_stats_tree_packet(stats_tree *st, /* st as it was passed to us */ packet_info *pinfo, /* we'll fetch the addresses from here */ epan_dissect_t *edt _U_, /* unused */ const void *p) /* we'll use this to fetch the ports */ { static guint8 str[128]; e_udphdr* udphdr = (e_udphdr*) p; /* we increment by one (tick) the root node */ tick_stat_node(st, st_str_udp_term, 0, FALSE); /* we then tick a node for this src_addr:src_port if the node doesn't exists it will be created */ snprintf(str, sizeof(str),"%s:%u",address_to_str(&pinfo->net_src),udphdr->sport); tick_stat_node(st, str, st_udp_term, FALSE); /* same thing for dst */ snprintf(str, sizeof(str),"%s:%u",address_to_str(&pinfo->net_dst),udphdr->dport); tick_stat_node(st, str, st_udp_term, FALSE); return 1; } WS_DLL_PUBLIC_DEF const gchar version[] = "0.0"; WS_DLL_PUBLIC_DEF void plugin_register_tap_listener(void) { stats_tree_register_plugin("udp", /* the proto we are going to "tap" */ "udp_terms", /* the abbreviation for this tree (to be used as -z udp_terms,tree) */ st_str_udp_term, /* the name of the menu and window (use "/" for sub menus)*/ 0, /* tap listener flags for per-packet callback */ udp_term_stats_tree_packet, /* the per packet callback */ udp_term_stats_tree_init, /* the init callback */ NULL ); /* the cleanup callback (in this case there isn't) */ } ----- END ------ the stats_tree API ================== every stats_tree callback has a stats_tree* parameter (st), stats_tree is an obscure data structure which should be passed to the api functions. stats_tree_register(tapname, abbr, name, flags, packet_cb, init_cb, cleanup_cb); registers a new stats tree with default group REGISTER_STAT_GROUP_UNSORTED stats_tree_register_plugin(tapname, abbr, name, flags, packet_cb, init_cb, cleanup_cb); registers a new stats tree from a plugin with the default group stats_tree_register_with_group(tapname, abbr, name, flags, packet_cb, init_cb, cleanup_cb, stat_group); registers a new stats tree under a particular stat group stats_tree_parent_id_by_name( st, parent_name) returns the id of a candidate parent node given its name Node functions ============== All the functions that operate on nodes return a parent_id stats_tree_create_node(st, name, parent_id, datatype, with_children) Creates a node in the tree (to be used in the in init_cb) name: the name of the new node parent_id: the id of the parent_node (NULL for root) datatype: datatype of the new node, STAT_DT_INT or STAT_DT_FLOAT. The only methods implemented for floats are averages. with_children: TRUE if this node will have "dynamically created" children (i.e. it will be a candidate parent) stats_tree_create_node_by_pname(st, name, parent_name, datatype, with_children); As before but creates a node using its parent's name stats_tree_create_range_node(st, name, parent_id, ...) stats_tree_create_range_node_string(st, name, parent_id, num_str_ranges, str_ranges) stats_tree_range_node_with_pname(st, name, parent_name, ...) Creates a node in the tree, that will contain a ranges list. example: stats_tree_create_range_node(st,name,parent_id, "-99","100-199","200-299","300-399","400-", NULL); stats_tree_tick_range(st, name, parent_id, value_in_range); stats_tree_tick_range_by_pname(st, name, parent_name, value_in_range) Increases by one the ranged node and the sub node to whose range the value belongs stats_tree_create_pivot(st, name, parent_id); stats_tree_create_pivot_by_pname(st, name, parent_name); Creates a "pivot node" stats_tree_tick_pivot(st, pivot_id, pivoted_string); Each time a pivot node will be ticked it will get increased, and, it will increase (or create) the children named as pivoted_string the following will either increase or create a node (with value 1) when called tick_stat_node(st, name, parent_id, with_children) increases by one a stat_node increase_stat_node(st, name, parent_id, with_children, value) increases by value a stat_node set_stat_node(st, name, parent_id, with_children, value) sets the value of a stat_node zero_stat_node(st, name, parent_id, with_children) resets to zero a stat_node Averages work by tracking both the number of items added to node (the ticking action) and the value of each item added to the node. This is done automatically for ranged nodes; for other node types you need to call one of the functions below to associate item values with each tick. avg_stat_node_add_value_notick(st, name, parent_id, with_children, value) avg_stat_node_add_value_int(st, name, parent_id, with_children, value) avg_stat_node_add_value_float(st, name, parent_id, with_children, value) The difference between the above functions is whether the item count is increased or not. To properly compute the average you need to either call avg_stat_node_add_value or avg_stat_node_add_value_notick combined tick_stat_node. The later sequence allows for plug-ins which are compatible with older Wireshark versions which ignores avg_stat_node_add_value because it does not understand the command. This would result in 0 counts for all nodes. It is preferred to use avg_stat_node_add_value if you are not writing a plug-in. avg_stat_node_add_value_int is used the same way as tick_stat_node with the exception that you now specify an additional value associated with the tick. avg_stat_node_add_value_float is used to compute averages of floats, for nodes with the STAT_DT_FLOAT datatype. Do not mix increase_stat_node, set_stat_node or zero_stat_node with avg_stat_node_add_value_int as this will lead to incorrect results for the average value. stats_tree now also support setting flags per node to control the behaviour of these nodes. This can be done using the stat_node_set_flags and stat_node_clear_flags functions. Currently these flags are defined: ST_FLG_DEF_NOEXPAND: By default the top-level nodes in a tree are automatically expanded in the GUI. Setting this flag on such a node prevents the node from automatically expanding. ST_FLG_SORT_TOP: Nodes with this flag is sorted separately from nodes without this flag (in effect partitioning tree into a top and bottom half. Each half is sorted normally. Top always appear first :) The same node manipulations can also be performed via generic functions: stats_tree_manip_node_int(mode, st, name, parent_id, with_children, value); stats_tree_manip_node_float(mode, st, name, parent_id, with_children, value); mode is an enum with the following set of values: MN_INCREASE MN_SET MN_AVERAGE MN_AVERAGE_NOTICK MN_SET_FLAGS MN_CLEAR_FLAGS You can find more examples of these in $srcdir/plugins/epan/stats_tree/pinfo_stats_tree.c Luis E. G. Ontanon.